Sensors have been used to monitor electrical energy flowing through an electrical power system. For example, traditional current transformers have been used to monitor current flowing through a bus-bar. A traditional current transformer includes a primary winding (coil) and a secondary winding. Energy is coupled between the windings by the time varying magnetic flux that passes through (links) both primary and secondary windings. When current in the primary coil changes, a voltage is induced in the secondary coil by mutual electromagnetic induction.
Referring to FIG. 1, a example conventional current transformer 10 is constructed by passing a single primary turn (a single power line conductor 12) through a well-insulated toroidal core wrapped with many turns of wire (secondary 14). These transformers are typically described by their ratio from primary to secondary and the primary winding is installed in series with the power line conductor 16.
Some current transformers are commonly used in metering and protective relaying in the electrical power industry to facilitate the safe measurement of large currents, often in the presence of high voltages. Insulation voltage of the current transformer represents the maximum insulation provided when connected to a power source. In a high voltage environment, some current transformers utilize significant electrical insulation to isolate the secondary winding 14 from the primary winding 12. Some typical current transformers are relatively large (e.g., measuring about 8×8×20 inches) and typically weigh in excess of 500 lbs. when properly insulated. Accordingly, structures of significant strength and size are used in some arrangements to support the current transformers from solid ground as well as providing electrical isolation. A typical support structure height of a current transformer ranges from 4 feet (e.g., for use in 115 kV applications) to 10 feet (e.g., for use in 500 kV applications) and additional space may be provided between the current transformer structure and other equipments in the installation.
Typical installations include use of insulated wires to transmit output signals of the current transformers (from the secondary winding 14) to other equipment, such as relay blocks and monitoring circuitry within a metering/relay house. Depending on the layout of the installation, a typical signal wire may be a few hundred feet.
As described below, at least some aspects of the present disclosure provide methods and/or apparatus for monitoring one or more characteristic of electrical energy flowing through electrical conductors of an electrical power system.